This application claims the benefit of a Japanese Patent Application No. 2001-028714 filed Feb. 5, 2001, in the Japanese Patent Office, the disclosure of which is hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to optical recording media, recording and reproducing methods and storage units, and more particularly to an optical recording medium such as a magneto-optical recording medium which uses magnetic super resolution (MSR), and to a recording and reproducing method and a storage unit which are suited for reproducing information from such an optical recording medium.
Recently, the recording densities of optical recording media have increased, and of the magneto-optical recording media such as the magneto-optical disk, there are recording media which were developed to use the MSR. In this specification, a recording medium which uses the MSR will be referred to as a MSR recording medium. When reproducing information from the MSR recording medium, it is desirable to obtain a stable reproduced output regardless of changes in temperature and laser power.
2. Description of the Related Art
For example, a Japanese Laid-Open Patent Application No. 7-29238 proposes a method which records a reference signal on a disk in advance, stores values such as a reproduced signal amplitude and a carrier-to-noise (C/N) ratio, and compares the reference signal which is reproduced from the disk and a reference value when the disk is loaded into a storage unit (disk unit) or the storage unit is started. According to this proposed method, a reproducing laser power is appropriately controlled to carry out a temperature compensation for cancelling a change in the magnetic characteristic caused by a temperature change at the time of the reproduction, based on a comparison result. In other words, the changes in the environmental temperature and the laser power are detected, and the laser power, the pulse width or the like are controlled based on the detected results.
Such a method is also proposed in Japanese Laid-Open Patent Applications No. 4-258831 and No. 7-262643.
However, the proposed method described above does not take into consideration the peculiar problems which are generated at the time of reproduction of the MSR recording medium. In other words, in the case of the MSR recording medium, even if the temperature at the time of the reproduction is the same, the optimum conditions such as the laser power and the reproducing magnetic field at the time of the reproduction differ if the temperatures at the time of the recording differ. Hence, unless the temperature at the time of the recording is known in advance, it is extremely difficult to obtain the optimum conditions for the reproduction. In addition, since the information recording with respect to the MSR recording medium is carried out at arbitrary timings, the temperatures at the time of the recording in many cases differ depending on the recording regions on the MSR recording medium, thereby making it further difficult to obtain the optimum conditions for the reproduction for each of the recording regions.
FIG. 1 is a diagram showing a relationship between a reproducing magnetic field and an error rate of a MSR recording medium for four different recording and reproducing conditions. FIG. 1 shows the reproducing magnetic field with respect to one track on the MSR recording medium for a case where the MSR recording medium is a disk. In FIG. 1, a solid line indicates the relationship for a room-temperature recording (hereinafter referred to as a write) and a room-temperature reproduction (hereinafter referred to as a read), a dotted line indicates the relationship for a room-temperature write and a high-temperature read, a one-dot chain line indicates the relationship for a high-temperature write and a high-temperature read, and a double line indicates the relationship for a high-temperature write and a room-temperature read. In this case, the room temperature is 25xc2x0 C., and the high temperature is 55xc2x0 C. Furthermore, H1 denotes a point of inflection (hereinafter referred to as an inflection point) for the room-temperature write and room-temperature read, H2 denotes a inflection point for the high-temperature write and high-temperature read, H3 denotes a inflection point for the room-temperature write and high-temperature read, and H4 denotes a inflection point for the high-temperature write and room-temperature read.
As may be seen from FIG. 1, in the case of the MSR recording medium, the optimum read conditions change when the write temperature changes, even if the read temperature is the same, and a relationship H1 less than H2 less than H3 stands. In addition, the values of the inflection points H1, H2, H3 and H4 change depending on the radial position on the MSR recording medium, production lot and the like of the MSR recording medium.
In the conventional magneto-optical disk unit, a test write and read is carried out with respect to a test track region on the magneto-optical disk, so as to determine a write laser power (hereinafter simply referred to as a write power), a read laser power (hereinafter simply referred to as a read power), and a reproducing magnetic field which are optimum. When determining such optimum values, a value which is obtained by adding a constant value xcex1 to the inflection point is regarded as the optimum reproducing magnetic field, by taking into consideration the inconsistencies in the read power and the reproducing magnetic field. This constant value xcex1 is obtained by actual measurement or calculation, by taking into account the effects such as the inconsistencies within one track on the magneto-optical disk and the crosstalk from the adjacent tracks.
However, when the reproducing conditions are determined by carrying out the test write and read with respect to the test track region, in the case of the room-temperature write and high-temperature read, it is only possible to obtain the inflection point H1 of the reproducing magnetic field for the room-temperature write and room-temperature read in FIG. 1 by the test read during the write, and the inflection point H2 of the reproducing magnetic field for the high-temperature write and high-temperature read in FIG. 1 by the test read during the read. The inflection point H3 of the reproducing magnetic field for the room-temperature write and high-temperature read shown in FIG. 1 and the inflection point H4 of the high-temperature write and room-temperature read shown in FIG. 1, which are actually required, cannot be obtained.
Similarly, when the reproducing conditions are determined by carrying out the test write and read of the reference signal in advance at the room temperature as in the proposed method described above, it is only possible to obtain the inflection point H1 of the reproducing magnetic field for the room-temperature write and room-temperature read shown in FIG. 1 by the room-temperature test read, and the inflection point H3 of the reproducing magnetic field for the room-temperature write and high-temperature read shown in FIG. 1 by the high-temperature test read. The inflection point H2 of the reproducing magnetic field for the high-temperature write and high-temperature read shown in FIG. 1, and the inflection point H4 of the reproducing magnetic field for the high-temperature write and room-temperature read shown in FIG. 1, which are actually required, cannot be obtained.
Accordingly, when the optimum values for the read power and the reproducing magnetic field with respect to the temperature at the time of the test read are obtained by the test read but the error rate is poor if the actual data read is carried out using these optimum values, it is possible to update the optimum values by carrying out a retry by changing the read power and the reproducing magnetic field. A method of updating the optimum values while carrying out the retry in such a manner is proposed in a Japanese Laid-Open Patent Application No. 2000-182292, for example.
However, if data having different write temperatures coexist on the magneto-optical disk, the retry is carried out frequently according to this method of updating the optimum values while carrying out the retry, and the retry time consequently becomes long. Normally, the data having the different write temperatures coexist on the magneto-optical disk in most cases, and the increase of the retry time cannot be avoided. On the other hand, the retry time is limited depending on a host unit which uses the magneto-optical disk unit, and the retry may be ended by a time-out if the retry is frequently generated.
In addition, when the method of updating the optimum values while carrying out the retry is applied to the MSR recording medium, the data itself may be erased if the read power at the time of the actual data read is set too large.
A description was given above with respect to the write conditions and the read conditions at the room temperature and the high temperature. The reproducing magnetic field with respect to the write temperature and the read temperature, including the low temperature, is as shown in FIG. 2. FIG. 2 is a diagram showing inflection points of the reproducing magnetic field which are plotted for a MSR recording medium different from that of FIG. 1. In FIG. 2, the ordinate indicates the magnetic field, and the abscissa indicates the read temperature. Moreover, symbols xe2x80x9cxe2x97xafxe2x80x9d, xe2x80x9c▪xe2x80x9d, xe2x80x9c▴xe2x80x9d, xe2x80x9c♦xe2x80x9d, xe2x80x9c*xe2x80x9d, xe2x80x9c*xe2x80x9d and xe2x80x9c|xe2x80x9d respectively indicate cases where the write temperature is 10xc2x0 C., 20xc2x0 C., 30xc2x0 C., 40xc2x0 C., 50xc2x0 C., 60xc2x0 C. and 65xc2x0 C. As may be seen from FIG. 2, a relationship H1  less than H2 less than H3 stands among an inflection point H1 for the room-temperature write and room-temperature read, an inflection point H2 for the high-temperature write and high-temperature read, and an inflection point H3 for the room-temperature write and high-temperature read.
In the case of the MSR recording medium, even if the reproducing temperature is the same, the optimum conditions such as the laser power and the reproducing magnetic field at the time of the reproduction are different if the temperatures at the time of the recording are different. As a result, there was a problem in that it is extremely difficult to obtain the optimum conditions for the reproduction unless the temperature at the time of the recording is known in advance. In addition, because the information recording is carried out with respect to the MSR recording medium at arbitrary timings, the temperature at the time of the recording differs depending on the recording region on the MSR recording medium in most cases, and there was another problem in that it is even more difficult to obtain the optimum conditions for the reproduction for each recording region on the MSR recording medium.
Accordingly, it is a general object of the present invention to provide a novel and useful optical recording medium, recording and reproducing method and storage unit, in which the problems described above are eliminated.
Another and more specific object of the present invention is to provide an optical recording medium, recording and reproducing method and a storage unit which enable satisfactory information reproduction by obtaining optimum conditions such as laser power and reproducing magnetic field for the reproduction, regardless of the temperatures during the recording and reproduction.
Still another object of the present invention is to provide an optical recording medium comprising a test track region corresponding to each zone, and a corresponding map portion of read test track region, wherein the test track region including a test track region portion which includes one or more test tracks to which a test write and a test read are carried out, and a temperature-based read test track region portion, the temperature-based read test track region portion includes one or more read test tracks, and a recording is made at an optimum write power for a write temperature during a write and a test read is made during a read so that at least an optimum reproducing magnetic field is set, and the corresponding map portion of the read test track region is recorded with an identification symbol which indicates a boundary of a map, a start address and an end address of the read test track for each write temperature information, a start address and an end address of each corresponding data, and an end identification symbol which indicates an end position of the map. According to the optical recording medium of the present invention, it is possible to realize a satisfactory information reproduction by obtaining optimum conditions such as the laser power and the reproducing magnetic field for the reproduction, regardless of the temperatures during the recording and reproduction.
A further object of the present invention is to provide a storage unit having functions of controlling a write power, a read power and a reproducing magnetic field with respect to an optical recording medium, comprising first means for storing test write data on the optical recording medium for each write temperature information during a write, and second means for controlling at least the reproducing magnetic field depending on optimum reproducing conditions which are obtained by reproducing the test write data corresponding to a write temperature of data which is to be actually reproduced from the optical recording medium during a read. According to the storage unit of the present invention, it is possible to realize a satisfactory information reproduction by obtaining optimum conditions such as the laser power and the reproducing magnetic field for the reproduction, regardless of the temperatures during the recording and reproduction.
Another object of the present invention is to provide a recording and reproducing method adapted to a storage unit which has functions of controlling a write power, a read power and a reproducing magnetic field with respect to an optical recording medium, comprising the steps of storing test write data on the optical recording medium for each write temperature information during a write, and controlling at least the reproducing magnetic field depending on optimum reproducing conditions which are obtained by reproducing the test write data corresponding to a write temperature of data which is to be actually reproduced from the optical recording medium during a read. According to the recording and reproducing method of the present invention, it is possible to realize a satisfactory information reproduction by obtaining optimum conditions such as the laser power and the reproducing magnetic field for the reproduction, regardless of the temperatures during the recording and reproduction.
Still another object of the present invention is to provide an optical recording medium comprising a test track region corresponding to each zone, where the test track region includes a corresponding map portion of a read test track region, a test track region portion, and a temperature-based read test track region portion, the test track region portion includes one or more test tracks to which a test write and a test read are carried out, the temperature-based read test track region portion includes one or more read test tracks, and a recording is made at an optimum write power for a write temperature during a write and a test read is made during a read, so that at least an optimum reproducing magnetic field is set, and the corresponding map portion of the read test track region includes an identification symbol which indicates a boundary of a map, a start address and an end address of a read test track for each write temperature information, a start address and an end address of each corresponding data, and an end identification symbol which indicates an end position of the map. According to the optical recording medium of the present invention, it is possible to realize a satisfactory information reproduction by obtaining optimum conditions such as the laser power and the reproducing magnetic field for the reproduction, regardless of the temperatures during the recording and reproduction.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.